Currently, enthalpy changes due to chemically reactive species are detected using bench laboratory equipment, as DSC (Differential Scanning calorimeter) or Photo-DSC analyzer. DSC equipment yield accurate information, but they can be big and expensive. Moreover, their operation may require skilled people and the performed analysis can be time-consuming.
The object of the invention is to provide a cheap and portable solution for the detection of specific markers that can be detected when dissolved in a liquid at low concentration, in particular in fuel liquids, such as refined petroleum products including gasoline, diesel, kerosene, etc. The markers preferably have a good solubility in the liquid, and are preferably difficult to be identified, extracted and separated. The proposed solutions preferably provide a fast and reliable detection of the presence of a marker in a liquid, such as liquid fuel.